Wired radio reception regulation



June 27, 1933. P, TA TZ I 1,915,768

WIRED RADIO RECEPTION REGULATION Filed March 1 1928 INVENTOR fiUL TAETZ BY flay/Mm A ORNEY Patented June 27, 1933 UNITED STATES PATENT" OFFICE" PAUL TAETZ, OF BERLIN, GERMANY, ASSIG-NOR T TELEFUNKEN GESELLSCHAFT Ilifi'ilitv DRAHTLOSE TELEGRAPHIE M. 131., OF BERLIN, GERMANY, A CORPORATION OF GERMANY WIRED RADIO RECEPTION REGULATION Application filed March 16, 1928, Serial No. 262,314,and in Germany March 29, 1927.

Wire-guided carrier telephony is attended, in practice, with certain technical difficulties which arise when the transmission line is subject to considerable Variations in damping. Such difiiculties are often caused by the formation of hoar, etc. Hence, it becomes necessary to provide equipment which will insure a practically constant receiving volume in spite of fluctuations in damping or line attenuation.

When connecting radio frequency equipment to ordinary postal wires by means of what is known as the split (duplex) connection, this problem assumes particular importance in 'sofar as the line attenuation between the apparatus should not be unduly low in order that disturbing backfeed by way of the forked connections in both equipments may beprecluded. Itis occasionally necessary, by establishing looser coupling of the receivers, to artificially raise the attenuation between transmitter and receiver so that even in the presence of optimum line attenuation, operationsmay be carried on'sufliciently far away from regeneration (whistling). An eflicient automatic regulation scheme, for the amplification factor, looked at from this viewpoint, would give the telephone equipment still further leeway respecting the admissible variations in line attenuation. v

To solve the problem, one method would be to simply operate the telephone receiver means, which, comprises essentially dem0d' by making the prevalent amplification fac-' tor of the telephone receiver dependent upon the amplitude of the incoming carrier-frequency potential varying with the line at.- tenuation. To insure the desired dependence of the amplification factor of the receiver upon the amplitude of the incoming carrier-frequency, recourse may be had to similar means as used in radio frequency telephone transmitters for regulating the input amplifiers, and for the prevention of overmodulation by variable voice intensity. (See, for example, German Patent, 445,- 575). Also, in the case of the regulating means here disclosed, in order to act upon the amplification factor, variable biasing potentials or feeble-current resistances can be employed in known manner. .The present invention is distinguished from prior automatic transmitter regulation methods,

in so far as the amplification of the receiver is automatically regulated, in dependence Y upon the potential of the incoming carrierwave. In this manner, an'automatic regulation of the receiver, in a satisfactory and distortionless way is'insured, a factor particularly important for wire-guided radio frequency telephony,

The desired action, either applied in a steadyor intermittent manner, of the regulative quantities governing amplification (gain regulators or biasing potentials) by the amplitude of the incoming carrier wave can be effected either directly by the aid of ielectrodynamic, electromagnetic or electrothermal instruments, one member of which is under the influence of the incoming carrier-wave potential, and whose other mobile parttakes care of the adjustment of such amplifier regulation quantities as may be required. However, since instruments of this kind consume comparatively much power, which is usually not available in wire-guided carrier-wave telephony directly at the entrance point of the receiver apparatus, it is a preferable plan in practice to first conveniently increase such regulation energy as has been absorbed for regulation purposes by the aid of suitable amplifiers. The most suitable idea is'to use tube circuits for amice .tion upon the regulation quantities.

For variable gain regulators and amplification control, instead of solid or liquid ohmic resistances, also tubes can be em ployed, in known manner, whose eflective resistance may be regulated in such a mannor, that the grid excitation is influenced in the required manner by the incoming carrier-wave potential.

It will be obvious that regulating means of the above nature will be useful and valuable not only for telephonic apparatus, but that this regulating method will prove of practical use also for telegraphy and telemechanical apparatus in which wire-guided radio frequency is employed.

The ideas underlying'the present invention are explained in the appended detailed description, reference being made to the accompanying drawing, in which Figs. 1, 2 and 3 schematically disclose three types of circuit embodying the present invention.

Fig. 1 shows a circuit arrangement for telephone equipment which is united with existent lines, say, high-potential lines H, by means of radio frequency repeaters or transformers (transformer Sw for the transmit ter, and transformer Euv for the receiver) or else through condenser C. The transmitter equipment is indicated by S, the receiver apparatus by E, while the ringing or calling means is denoted by E. The transmitter S and the receiver E are connected with the audio'frequency line La, Lb through the known forked (split) scheme comprising differential transformer D and line simulation N. The radio frequency equipment above referred to is indicated only in a simple diagrammatic way, because it is generally known and does not form part of the present disclosure. According to the invention, the receiver E is automatically regulated by the igcoming carrier-wave potential denoted by In the form of construction shown, this regulation is effected through the agency of a gain regulator (potentiometer) R which in this case is connected in parallel with the output terminals of the receiver E. The incoming carrier-wave potential V is transferred either directly, or, as shown, by way of a transformer U to the grid circuit of a rectifier tube GZ, thereby influencing the plate current of this tube, the latter flowing, if desired, through the stationary coils ofan electrodynamic or electromagnetic instrument J.

By means of the condenser C and the choke-coil D the regulative rectifier effect remain-s unaffected by transient carrier-wave fluctuations during the call, ring or modulation. The gain regulator B is shown constructed in the form of a liquid rheo-stat whose stationary electrode 0 is connected with one of the output terminals, and whose other adjustable electrode 6, subject to control by the mobile part a of the instrument J, is united with the other output terminal of the receiver.

It will be understood that the gain regulator R could be designed also in some other Way; for example, as a fixed resistance or else as a tube resistance, and instead of being connected with the output terminals, the same could also be associated with any of the grid circuits of the receiver equipment.

In the form of construction shown in Fig. 2, the transmitter, the calling device of the receiver, and the telephony wires have not been shown for the sake of simplicity and the receiver E has been assumed to consist of two tubes 1 and 2. The rectifier tube GZ, asin the previous embodiment, is influenced by the carrier-wave potential V through the transformer U, and the electro-magnetic instrument J, passed by the direct current is here a solenoid which actuates a contact movable along the potentiometer P. In this way, such part of the potential supplied from the battery R1), as is required for regulation, is applied in the form of a variable biasing potential in the grid circuit of input tube 1 of the receiver apparatus, suitably in parallel relation to a condenser C Of course, the receiver can comprise a plurality of stages, and the biasing potential can be controlled in other stages as has hereinbefore been described. Either conjointly with, or else instead of, regulation of biasing potential, a rheostat, or variable resist ance, can be controlled or adjusted as before set forth, in the grid circuit of any desired stage. In the case of Fig. 2, this idea is shown by the variable resistance R2 in the grid circuit of the output tube 2, and the same may consist of a solid, liquidor a tube resistance as abovepointed out.

Fig. 3 shows how the fall of potential across a resistance J may be utilized for the purpose of regulating the receiver apparatus. In this arrangement, the plate current of the rectifier GZ, connected in a manner similar to the previous circuit arrangements, is made to flow through the resistance J whose terminals are connected in the grid circuit of a receiver tube, say, the input tube 1.

Having thus described my invention what I' desire to protect by Letters Patent is as follows:

1. In a wired radio receiving system, a

transmitting line over which the incoming,

carrier is transmitted to the receiver, the attenuation of the said transmitting line being variable under diflerent conditions, a receiver including an amplifier upon which the carrier wave is impressed, an electronrier current for transmitting signals over the transmission line to the receiver, the attenuation of the transmission line being variable under different conditions, the receiver including an amplifier upon which the modulated carrier wave is impressed, an

electron discharge t tube rectifier connected to said line and having a portion of said carrier wave impressed upon its input terminals, a capacitive reactance connected between the input terminals of the amplifier, a potentiometer connected across said capacitive reactance, and means including an inductive reactance in the output circuit of said rectifier toadjust said potentiometer in accordance with the amplitude of the direct current component of the rectified carrier current to compensate for changes in line attenuation. PAUL TAETZ. 

